For the Eustachian tube function testing, the subject and a technician are seated comfortably within a pressure chamber, a room-like chamber in which the air pressure can be varied much like in an airplane or submarine. Middle ear pressure will be measured in each ear by tympanometry, a test done by inserting a small probe (an earplug attached to a rubber or plastic tube that measures ear pressure) half-way into the ear canal and changing the pressure in the probe. Then, microphones will be placed in the ear canals and a sound source placed into one nostril. The chamber pressure is then decreased and increased to various pressures and middle ear pressure is measured at these various pressures.